From the viewpoints of energy problems and environmental problems, efficient CO2 reduction utilizing light energy similar to that performed by plants is in demand. Plants use a system called “Z-scheme” in which the light energy is excited in two stages. In the photochemical reaction using the system, water (H2O) is oxidized to give electrons, and carbon dioxide (CO2) is reduced to cause synthesis of celluloses and sugars.
At present, artificial photosynthesis systems for obtaining potentials required for reduction of CO2 in imitation of the z-scheme by plants are under development.